The different characteristics of voice and data information compound the problems of switching both types of information in the same switching system. There are two distinct characteristics of data communications which distinguish it from voice communication and which make the use of dedicated voice channels for data inefficient. In general, data is transmitted in short, high-rate bursts with long pauses in between bursts. The second characteristic is that, in many data applications, there is a very low average data rate compared to the data rate required for voice communication.
Known packet switching provides a solution to these problems by collecting a burst of data in one or more packets, each of which can be moved through the switching facilities at a rate convenient for the switching system. A packet consists of a predetermined number of data bytes, together with synchronization and other identifying data such as a header. The packet is a unit of data which can be moved, stored and otherwise manipulated through the system and has the desirable characteristic that it allows the system to transmit the packets at a data rate which is well suited for the efficiency of the system.
It is highly desirable for voice and data communication switching to be provided by one integral system so as to increase the flexibility and efficiency of the switching functions. Prior art systems customarily use two distinct subsystems in order to switch data packets and voice signals. In one such arrangement, the data and voice are separated at the input to the system and then the voice is switched by one switching subsystem while the packets are gathered and switched by another. In another prior art system, data is first converted from digital signals to modulated analog signals having frequencies similar to those of the human voice. The voice and modulated analog data signals are then switched through a voice network with the modulated analog data signals being connected to a separate packet switching subsystem.
Such prior art systems for switching packets and voice are deficient in that they require, in reality, two distinct systems. The use of two distinct systems have proven to result in higher cost and complexity to both communication companies and their customers.
In view of the foregoing, there exists a need for a communication system which has the capability of interconnecting both voice and data terminals through a single communication switching system with efficiency and without prolonged dedication of communication channels for the integrated data and voice communications.